<html xmlns="http://www.w3.org/1999/xhtml">
  <head>
    <style><![CDATA[
      .green { color: green; }
      .toremove { color: red !important; }
    ]]></style>
  </head>
  <body>
    <div class="foo toremove">
      This should be green
    </div>
    <script>
      var div = document.getElementsByTagName("div")[0];
      div.classList.toggle("toremove");
      div.classList.toggle("green");
    </script>
  </body>
</html>
